View or print this publication - Northern Research Station - USDA ...

Pine
tn pine species the new needles emerge rather late in spring. Old needles are tough and of low nutritive value. This
means that there is a long period with few feeding opportunities for herbivores, except for the existence of male inflorescences.
In most places, pines set flower buds much more consistently than do spruce.
New pine needles are less nutritive than spruce, nitrogen reaches only 2-2.5% of dwt. The toxins occurring in new
needles are potent and it has been demonstrated (Ikeda et al. 1977) that they reduce growth rate, increase mortality, and
extend larval period. Not surprisingly, most defoliator species feed on old needles or current year needles late in the year
(Larsson and Tenow 1980, Table 4).
Table 4.--Needle age preferences of insect larvae feeding on Scots pine, Pinus sylvestris.
Insect species Needle age class
Current Old
Lepidoptera
Bupalus pM[aria * *
Cedestis spp *
Cidaria firmata *
Dendrolimus pini * *
Ellopia fasciaria *
Hyloicus pinastri *
Panolis flammea * *
Semiothisa liturata *
Lymantria monacha *
Hymenoptera
Diprion pini * *
Diprion ximilis *
Gilpinia frutetorum *
Microdiprion pallipes * *
Neodiprion sertifer *
Nun moth larvae normally hatch prior to bud-burst, leaving them with only old pine needles for food. Experiments in
field enclosures and in the laboratory with first instar larvae on whole branches or twigs, showed almost 100% mortality.
Only if the bagged branches included male flowers were larvae able to survive. In the laboratory, larvae survive and develop
only if they are put on flowering branches in the first part of their life, irrespective of pine species (P contorta, P. sylvestris,
P. mugo) (Table 5). Surviving larvae that later were fed new or old needles, performed equally well (Fig. 2).
Table 5.--Percent survival of nun moth larvae on pines. T = 17 days, n = 85 per trial.
P. silvestris P. mugo P. contorta
Flowering 71.0 50.8 14.6
Non-flowering 15.0 16.7 0.0
107